A dishwasher having an ion exchanger and a salt container is known from German Patent Application DE 102 04 548 A1.
To prevent lime deposits on the dishes, it is known to soften the raw water flowing into the washing tub of a dishwasher using an ion exchanger. In household dishwashers, the ion exchanger generally contains a mixed bed resin whose softening components become exhausted and then have to be regenerated by a solution of common salt. To accommodate a supply of salt that lasts for several regeneration cycles, a water softener therefore contains a salt container in addition to the ion exchanger. In commercial dishwashers, it is generally known and a common practice to arrange the salt container in the bottom space of the appliance housing and to fill it through an opening in the bottom plate of the washing tub. However, this is uncomfortable for the user because he/she must reach far into the washing tub. An even greater disadvantage arises if a lack of salt is noticed when the appliance is loaded. In this case, it is first necessary to unload the lower dish rack to be able to remove it from the washing tub, and to thereby gain free access to the fill opening of the salt container. To avoid these disadvantages, German Patent Application DE 102 04 548 A1 proposes to arrange the salt container in the appliance door, thereby allowing it to be easily filled through an opening on the inside of the door. Due to the small amount of space between the outside door panel and the inside door panel, such a salt container must have a very flat design. To nevertheless allow the container to hold a quantity of salt sufficient for about 10 to 15 regeneration cycles, the container is designed to extend over a large area, that is, in addition to a sufficient width, it also has a large height. This affects the flow conditions in the salt-filled container.
In the dishwasher known from German Patent Application DE 102 04 548 A1, the salt container is divided into a salt chamber and a water inlet by a screen which is located horizontally when the door is closed. In the region above the salt, a brine chamber is formed into which opens a brine outlet. In particular, if fine-grained salt (fine salt), such as commercially available common salt, is used for regeneration, the vertical flow through the salt chamber leads to a heavy compaction of the salt, causing obstruction of the screen.
In dishwashers with salt containers in the appliance housing, it is also known to divide the salt container into a salt chamber and a brine chamber by a screen. However, here, the brine outlet does not open into the salt chamber, but, together with the water inlet, into brine chamber underneath the screen. In this context, the water inlet and the brine outlet are located on opposite sides of the brine chamber. For regeneration, a supply amount of water corresponding to the required quantity of brine is admitted to the brine chamber. The salt lying on the screen is dissolved by this raw water from below, as a result of which a brine with the desired concentration forms in the brine chamber. The next time raw water is introduced, this brine is forced into the ion exchanger. This principle can only work in the case of relatively low salt heights and screens having a very large surface area. In the case of narrow screens and high salt heights, clogging would be inherent, as described further above. Moreover, a relatively constant brine concentration can only be achieved if the brine chamber volume can hold the quantity of brine required for a regeneration cycle. In the case of the narrow salt containers in the door, this would be at the cost of the salt supply and is therefore not possible.
In dishwashers with salt containers in the appliance housing, it is also known to mount two right-angled screens in the bottom space, the screens dividing the salt container into a salt chamber and two brine chambers, and the salt chamber extending into a so-called “salt trench” between the two vertical screen walls. Since the fluid flow through the salt trench is in a horizontal direction, the salt concentration is increased. The use of such screens in a high, flat salt container is not practicable. When the salt level is high, the horizontal screens become clogged, and the salt is dissolved only in the region of the salt trench. Only a small amount of additional salt slides down over the right-angled edge, which results in a subsequent decrease in the salt concentration. When the salt level is low, water is also flushed through the horizontal screens because these screens are now no longer clogged. This results in a sharp increase in the brine concentration. Consequently, the known screen system with salt trench causes a considerable variation in concentration.